The circadian health coach · iOS · private beta
Align your biology
Align your day with your biology. Sunlight, sleep, fasting and grounding — connected by your circadian rhythm.
An invite when the beta opens. Nothing else.
Your day has a shape
Light, sleep, meals and rest follow the same 24-hour clock. biokei reads your day against that clock and suggests the next thing that brings you back into rhythm.
Sunlight
Know your dose of sun
Time in Daylight comes from Apple Health. On top of it, biokei models your UV dose and vitamin D and shows both on a dual dosimeter: burn risk on one side, vitamin D benefit on the other.
The two sides move at different speeds — more skin in the sun raises vitamin D without raising burn risk the same way. The dosimeter makes that trade visible, so you can take the benefit and skip the burn.
UV dose and vitamin D are estimates from a model — the app labels them that way.
Sleep
Sleep anchors the whole day
Duration, stages, resting heart rate and HRV — synced automatically from Apple Health, nothing to log. Sleep is the anchor the rest of your rhythm is read against: when you wake sets when to seek light, when to eat, when to wind down.
Track your cycles
A session runs quietly in the background — on your lock screen, in the Dynamic Island, on a widget. You see where you are in the cycle at a glance, without opening the app.
Achieve goals
Each day closes with a simple score across your four domains. The bar fills as your day does — no streaks to protect, just a week you can see taking shape.
Fasting
An eating window, kept gently
A simple eating-window timer with a Live Activity and a widget, so your window is visible without opening the app. What matters is that meals land at a consistent time of day — in rhythm with everything else.
biokei never rewards longer fasts. No streaks, no records, no leaderboards. You can break your fast anytime you need to — comfort comes first.
Grounding
ExperimentalGrounding, honestly labelled
Evidence for grounding is limited and early. We include it because some people find it calming — simple session logging, so you can track how it feels for you. The label says experimental because that is what it is.
We label down, never up
Most health apps blur the line between what a sensor measured and what an algorithm guessed. biokei keeps the line visible — it's the point of the product.
Measured
Sleep duration and stages, resting heart rate, HRV and Time in Daylight — read from Apple Health, straight from your devices.
Modelled
UV dose and vitamin D are estimates from a model of weather, location, skin type and clothing. Every modelled number in the app is marked est.
Experimental
Grounding carries an experimental label because the evidence is limited and early. We say so in the app, and here.
Why "biokei"
Kei (系) is Japanese for "system" or "lineage". biokei is your biological system — the one rhythm your sleep, light, meals and rest all belong to. Pronounced "bio-kay".
Made by Biokei Labs.
Get early access
biokei is in private beta. Leave your email and you'll get an invite when it opens — that's all we'll send.